Direct Observation of Sub-100 nm Silica Particle Detachment: Lateral Force and Evanescent Microscope Study

It has been difficult to detach smaller abrasive particles from the polished surfaces. In the cleaning phenomenon, the shear force acts on the residual nano-particles on the substrate in the shear flow. In order to understand the cleaning mechanism, it is indispensable to investigate the detachment characteristics that correspond to nano-particle diameter by verifying not only the force but also the energy interaction such as bonding. Here, we verify that the energy required to detach the silica nano-particles from the oxide film surface was determined by measuring the lateral force acting on the nano-particle in dry/wet conditions using lateral force microscopy. Moreover, the detachable diameter of the nano-particle was experimentally investigated using an evanescent light to estimate the required shear flow velocity near the surface, which inevitably occurred in the cleaning process. These results implied that larger-sized nano-particles could be detached when the shear force acting on the nano-particle is sufficient compared with the shear force/energy required to detach from the surface related to the potential energy of hydrogen bond.